Six British soldiers have been killed while on on patrol in Helmand province in southern Afghanistan.
The Defence Ministry says their armoured vehicle was hit by an explosion on Tuesday.
An Afghan police official says the blast was caused by a roadside bomb, the deadliest weapon used by insurgents.
The incident marks the biggest single loss of life for British troops in Afghanistan in six years.
Five of the soldiers were from the 3rd Battalion the Yorkshire Regiment and one from the 1st Battalion The Duke of Lancaster's Regiment.
The deaths take the toll of British service personnel to 404 since the American-led invasion to oust the Taliban began in 2001.
Britain is the second largest contributor to the NATO-led war after the United States.